The present invention relates to a pulley useable in power transmissions of vehicles and industrial equipments, and more specifically to a pulley useable with a V-shaped driving belt in a continuously variable transmission (CVT) of vehicles and the CVT using the pulley.
Among the conventionally proposed power transmissions of vehicles and industrial equipments, there are known two types of transmissions adapted to variably transmit revolutions through an input shaft to an output shaft. One type of transmissions is a gear train type including a plurality of meshing gears and the other type is a belt-driven CVT including a driving belt.
The belt-driven CVT conventionally proposed includes an input pulley connected with a power source such as an engine, and an output pulley drivingly connected with the input pulley through an endless driving belt that is disposed therebetween and made of metal. The pulleys each define V-shaped grooves in which the driving belt is located. The width of the V-shaped groove of each pulley is variable in a direction of a revolution axis of the pulleys. The revolution of the input pulley is continuously variably transmitted to the output pulley depending on continuous variation of the widths of the V-shaped grooves of the pulleys. The CVT of this type is disclosed in "C4 Automatic Transaxle" of New Model Car Manual titled "NISSAN Primera Primera Camino" published in September, 1997.
There has conventionally been proposed a pulley for the belt-driven CVT. The pulley is made using a workpiece made of a case hardening steel. The workpiece is subjected to carburizing-quenching and tempering, and then to grinding so as to form on the outer circumferential periphery, contact surfaces that are in contact with the belt when the belt is placed in the V-shaped groove of the pulley.
There is also known an endless driving belt for the CVT, that includes a multi-layered ring composed of a plurality of ring-shaped bands laminated on one another and a plurality of V-shaped elements continuously arranged side-by-side along the circumferential direction of the multi-layered ring. Each of the V-shaped elements has side faces that are in contact with the contact surfaces of each of the pulleys upon the driving belt being engaged with the V-shaped groove of the pulley. The V-shaped element is produced from a workpiece made of a suitable steel selected from carbon steels or alloy steels used for machines, carbon tool steels, alloy tool steels and the like. In the production of the V-shaped elements, the workpiece is subjected to a suitable heat treatment such as quenching and tempering, carburizing-quenching and tempering, carbonitriding-quenching and tempering, induction-hardening and tempering, induction-hardening and the like. U.S. Pat. No. 5,011,461 discloses a driving belt used in the belt-driven CVT. The driving belt includes an endless carrier with transverse elements disposed on the endless carrier. The transverse elements are provided with side faces mating with contact surfaces of the pulleys that define the V-shaped grooves therebetween, respectively. The side faces are formed with ridges and grooves. The ridges and grooves extend straightly or slantly relative to the longitudinal direction of the endless carrier. This arrangement is provided for discharging oil and restraining slip caused by an oil film that is formed between the contact surface of each pulley and the side face of each transverse element.